gravity filter question

The greater the elevation difference between the "dirty" water and the filter the better. I hang my "dirty" reservoir about 5' off the ground. The filter and the "clean" reservoir just lay on the ground. Filter to "clean" doesn't matter. And just as a sanity check – you are using a bladder (versus a hard bottle) for the clean water – right?

If the entire length of tubing is full of water, before and after the filter, then, no, it does not matter where the filter element it – differential pressure across the filter element then only depends on the elevation difference of the dirty and clean reservoirs (less frictional losses in the tubing). If, however, the tubing below the filter element has air in it (with some water trickling through; then you want the filter as low in elevation as you can get it. Higher never helps. Lower may help and avoids having to confirm that the downstream tubing is full of water and/or having to "burp" and air out the lower tubing.

Thanks Greg, To answer you question both. I will use it to fill either a badder or water bottles depending on the trip. I also will leave it up in camp for clean water as needed for whatever.

"I will use it to fill either a badder or water bottles depending on the trip. " As long as the fill tube is going into an open top bottle you'll be ok. Some folks have tried to fill a bottle via a nippled cap…. with little success. The air displaced by the incoming water needs to get out somehow. Have fun out there.

Thanks David, You always have the tech answers :)